This application is based on Patent Application No. 2001-012089 filed Jan. 19, 2001 in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a card connector to be attached to an electronic equipment such as a cellular phone, a telephone, a PDA (personal digital assistance), a portable audio or a camera, and an elastic contact piece built-in in the card connector. More specifically, it relates to a contacting structure thereof improved in impact-resistance and vibration-resistance to be free from instantaneous electric break.
2. Description of the Related Art
In an electronic equipment such as a cellular phone, a telephone, PDA or a digital camera, various capabilities can be extended by inserting an IC card such as an SIM (subscriber identity module, a trade mark) card, an MMC (multi-media card, a trade mark), a SMART MEDIA (a trade mark), an SD (secure digital) card or a MEMORY STICK (a trade mark) in which a memory or other control circuit is mounted therein.
In a connector structure for detachably mounting such an IC card onto the electronic equipment, a plurality of contact terminals formed of metallic spring pieces are accommodated in the interior of a connector housing. These contact terminals are respectively brought into contact with a plurality of contact pads formed on a front or back surface of the loaded IC card, whereby an IC in the IC card is electrically connected with the electronic equipment to which the connector is attached.
The plurality of contact pads of the IC card include a power source pad to be connected to an power source line and a plurality of signal pads for inputting and outputting various signals. These pads are connected via the plurality of contact terminals of the card connector to an power source circuit and various signal processing circuits in the electronic equipment.
The card connector used for such a portable and small-sized electronic equipment has a problem in that when the impact or vibration is applied to the card connector with a card being loaded therein, for example, by the fall of the equipment, the contact pad of the card may be apart from the contact terminal of the connector to cause an instantaneous break of electric conduction.
If such an accident occurs during the writing of data from the electronic equipment to a memory of the card, the data now being written may be lost or data stored in the card may be damaged or, in the worst case, there is a possibility in that the memory card itself may be broken.
For instance, when the contact terminal for signal is separated from the contact pad of the card, the continuity of data is cut off. A controller for the card, however, determines that the written data is incorrect and thus discarded the same.
When the contact terminal for an power source is separated from the contact pad of the card, an electricpower supplied to the controller is also disconnected. At that time, the controller for the card is in a state wherein all the processings are impossible. For example, a memory area of the card may be damaged if the written data has the continuity.
To solve such a problem, one may consider increasing a contact pressure of the spring piece constituting the contact terminal so that a force for retaining the card becomes larger. However, the above method is problematic in that since a operative force necessary for inserting/withdrawing the card increases in the same ratio as the contact pressure, the operability of card insertion/withdrawal becomes worse.
In this regard, one of causes of the electric break between the card and the connector due to an impact according to the fall of the electronic equipment or others is vibration and resonance. That is, when the impact is applied to the electronic equipment by the fall of the electronic equipment or others, a housing of the electronic equipment or a printed circuit board accommodated therein bends. The restoration force of printed circuit board or the like cause the interior parts of the equipment to vibrate.
If the frequency of this vibration coincides with a resonance frequency of the spring piece of the contact terminal, the spring piece of the contact terminal more largely vibrates to cause the contact to be separated from the contact pad, whereby the electric contact of the card with the connector may be broken.
The present invention has been made with reference to the above-mentioned circumstances, and a problem to be solved thereby is to provide a card connector capable of maintaining a proper contact pressure with a card within a limited space and of preventing the instantaneous electric break from occurring due to the impact or vibration.
In one embodiment of the present invention, a card connector is provided, which comprises a plurality of contact terminals, each having a terminal section to be connected to a printed circuit board, a fixing section to be secured to a connector housing and a spring piece section having a contact point section at a distal end thereof and bent to be elastically deformable, for holding an IC card within the connector housing so that, when the IC card is loaded therein, a plurality of contact pads are brought into contact with the contact point sections of the plurality of contact terminals, respectively, arranged in the connector housing, wherein the spring piece section of the contact terminal is split into a plurality of spring piece units, each split spring piece unit having a bending section not coinciding with that of the other, and a pressed portion against which is pressed a portion of the spring piece unit extending to the fixing section from the bending section in the split spring piece unit is arranged in the connector housing.
According to the present invention, since the spring piece section of the contact terminal is split into a plurality of spring piece units, wherein each split spring piece unit has a bending section not coinciding with that of the other, and a pressed portion against which is pressed a portion of the spring piece unit extending to the fixing section from the bending section in the spring piece unit is arranged in the connector housing, lengths of portions of the respective spring piece units functioning as a spring become different from each other, it is possible to differentiate a mass, a spring constant and a contact force thereof with the contact pad of the card between the respective split spring piece units. Thus, it is possible to differentiate the resonance frequencies (natural frequencies) of the respective spring piece units from each other.
Since the resonance frequencies of the respective split spring piece units are different from each other in the present invention, even if one of the split spring piece units of the contact terminal resonates due to the vibration of the electronic equipment caused by the fall impact to separate the same from the contact pad of the card, the other of the split spring piece units does not resonate to maintain the contact thereof with the contact pad. In other words, according to the present invention, it is possible to shift the timing at which the respective spring piece unit is separated from the contact pad upon the generation of impact or vibration.
Thus, even if a large impact or vibration is applied, the card inserted into the card connector can be maintained in a stable state free from the instantaneous electric break, whereby the possibility of loss of written data and stored data can be minimized.
Further, in the present invention, since each split spring piece unit has a bending section not coinciding with that of the other, and a pressed portion against which is pressed a portion of the spring piece unit extending to the fixing section from the bending section in the spring piece unit is arranged in the connector housing, it is possible to shorten a length of a portion in some of the split spring piece units functioning as a spring and thus increase the spring constant thereof. Accordingly, it is possible to increase the contact pressure of these split spring piece units with the card, whereby even if the connector is small in size, the card can be held with a proper contact pressure.
In the present invention, a width of the contact point section in some of the spring piece units may be larger than that of the spring piece section.
In the present invention, at least one of a mass, a spring constant and a contact force of the respective split spring piece unit with the contact pad of the card may be differentiated from that of the other by changing a width, a length of the split piece unit or a bending angle of the spring piece section.
According to another embodiment of the present invention, a card connector is provided, which comprises a plurality of contact terminals, each having a terminal section to be connected to a printed circuit board, a fixing section to be secured to a connector housing and a spring piece section having a contact point section at a distal end thereof and bent to be elastically deformable, for holding an IC card within the connector housing so that, when the IC card is loaded therein, a plurality of contact pads are brought into contact with the contact point sections of the plurality of contact terminals, respectively, arranged in the connector housing, wherein the spring piece section of the contact terminal is split into a plurality of spring piece units; each split spring piece unit bending so that the bending section is located by the side of the distal end thereof from the fixing section in the spring piece unit, and a pressed portion against which is pressed a portion of one of the plurality of spring piece units extending to the fixing section from the bending section in the spring piece unit is arranged in the connector housing, and a portion of the other spring piece unit extending to the fixing section from the bending section is in a free state.
According to the present invention, since the spring piece section of the contact terminal is split into a plurality of spring piece units, wherein each split spring piece unit bends so that the bending section is located by the side of the distal end thereof from the fixing section, and a pressed portion against which is pressed a portion of one of the plurality of spring piece units extending to the fixing section from the bending section is arranged in the connector housing, and a portion of the other spring piece unit extending to the fixing section from the bending section in the spring piece unit is in a free state, lengths of portions of the respective spring piece units functioning as a spring are different from each other, and it is possible to differentiate a mass, a spring constant and a contact force with the contact pad of the card between the portions of the respective spring piece units functioning as a spring. Thus, the resonance frequencies (natural frequencies) of the respective split spring piece units can be differentiated from each other. Accordingly, since either one of the plurality of spring piece units is always brought into contact with the card even if impact and vibration generate, whereby it is possible to prevent the instantaneous electric break from occurring between the contact terminal and the card.
As described above, according to the inventive card connector, since the spring piece section of the contact terminal is split into a plurality of spring piece units, wherein each split spring piece unit has a bending section not coinciding with that of the other, and a pressed portion against which is pressed a portion of the spring piece unit extending to the fixing section from the bending section is arranged in the connector housing, it is possible to prevent the instantaneous electric break from occurring between the contact terminal and the contact pad of the card when impact or vibration is applied, as well as to readily obtain a proper contact pressure between the contact terminal and the contact pad of the card even if space is limited.
Also, according to the present invention, since the spring piece section of the contact terminal is split into a plurality of spring piece units; each split spring piece unit bending so that the bending section is located by the side of the distal end thereof from the fixing section in the spring piece unit, and a pressed portion against which is pressed a portion of one of the plurality of spring piece units extending to the fixing section from the bending section is arranged in the connector housing, and a portion of the other spring piece unit extending to the fixing section from the bending section is in a free state, it is possible to prevent the instantaneous electric break from occurring between the contact terminal and the contact pad of the card when impact or vibration is applied, as well as to readily obtain a proper contact pressure between the contact terminal and the contact pad of the card even if space is limited.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.